How to change size of logo in header?

Hi guys,
To change the size of logo in header, please do as the following: 
Step1: you can log in to Dashboard > Theme > Customize > General Settings then add the following code to the “Header code”

 <style>
.site-header #header {
    background: none;
}

#branding {
    width: 800px !important;
}

.site-header #branding a {
    width: 800px;
    height: 80px;
}
</style>  

Step2: Select Title & Tagline, upload a logo image with the size of 800x80px

Step3: Move through Appearance > Widget > Header, remove the Text widget.
 
Hope this helps!